1908.] GENUS OF AMPHIPOD CRUSTACEA. 397 



or more joints of the perteopods and the peculiar torsion of the 

 first gnathopod. Tliis toi'sion is caused by the curvature of the 

 fourth and fifth joints, by whicli tlie normal position of the hand 

 and finger is reversed. Even in the young T. raschii taken from 

 the incubatory pouch a slight curvature can be seen, and the 

 immature specimen, 9 mm. in length, shows it already completed. 

 All the adult specimens of T. raschii yet discovered are females, 

 and all have this toi'sion. In T. nicceense some specimens show 

 it and others not. Costa's specimens are figured v^ith the hand 

 normal ; Delia Yalle records his three specimens, all males, with 

 the torsion ; Brian's specimen, ovigerous female, normal ; Ohev- 

 reux's, ovigerous female, with the hand twisted ; while the 

 ' Huxley ' specimen is an ovigerous female, and normal. In the 

 six taken by Mr. Tattersall, three males and three females, the 

 way the hand is held can be plainly seen. The second joint 

 of the first gnathopod is long and much curved ; the third or 

 elbow makes an acute bend forward ; the fourth bends back 

 towards the second ; and the fifth turns a little forward and 

 outwards in such a way as to hold the sixth joint or " hand " with 

 its inner side uppermost, so that the claw and curved spines 

 are on top, and the articulation of the claw appears to be in 

 the infero-posterior angle instead of the infeio-a uteri or angle as 

 in the normal position. The " hand " is enormously inflated, and 

 subquadrate. It is carried usually with the claw articulation 

 outwards and a little raised, the tips of the claws meeting under 

 the animal. All the joints are strengthened with ridges of chitin, 

 and all their margins are remarkably strong and thick. The 

 animal is evidently able to turn the hands in any direction at 

 will ; this can be plainly seen in Mr. Tattersall's specimens. In 

 one or two both hands are normal ; in one S23ecimen one hand is 

 normal and the other twisted, in the othei'S the hands are in the 

 position just described — these diflerences being evidently due to 

 the animal's contortions when being pi-eserved. 



Another peculiarity of this genus is the inflation of one or more 

 joints of the perasopoda : in T. raschii the foui'th joint of the first 

 and second perpeopods ; in T. nicceense the second joint of the first 

 and second perseopods ; and in Mr. Stebbing's new species the 

 sixth joint of the fifth joerfeopod. 



The sensory equipment of these animals is remarkable, thei-e 

 being no less than tw^enty-five specialised forms of set^e, four of 

 which are peculiar to the antennae, five to the oral parts, four to 

 the second gnathopoda, one to the incubatory lamellae, four to the 

 pleopoda, and one to the telson. As the number and arrange- 

 ment of the setfe appear constant, I have thought it well to oive 

 them in detail. 



The chief diflerences in the three species hitherto Jaiown lie in 

 the shape of the 2nd, 3rd, and 4th side-plates, the antenna?, the 

 2nd and 4th joints of the anterior perseopods, the 2nd joints of 

 the hinder perreopods, and in the telson. In the adult T. nicceense 

 the telson is entire ; in T. raschii deeply incised in the young and 



